import matplotlib.pyplot as plt
import numpy as np

# 次坐标轴
x = np.arange(0, 10, 0.1)

y1 = 0.05 * x**2

y2 = -1 * y1

fig, ax1 = plt.subplots()
ax2 = ax1.twinx()
ax1.plot(x, y1, 'g-')   # green, solid line

ax1.set_xlabel('X data')

ax1.set_ylabel('Y1 data', color='g')

ax2.plot(x, y2, 'b--') # blue

ax2.set_ylabel('Y2 data', color='b')
plt.show()